I'm not sure what either of you is saying here. C-c C-j works very
simply: the little help window pops up but the key sequences (arrows
and TAB basically) allow me to move in the original buffer until I hit
RET at which point the popup disappears and I'm in the original buffer
at the new location.

Am I missing something?

When I did that, it started with all of the headings closed. If I'm looking for something nested, it's VERY hard to use, or, I am doing something wrong. See how easy it is for you to find something at level 3, for example.